Test for brake fluid age and condition

Abstract

A correlation is derived between a variable, defined as “virtual age,” indicative of brake fluid's service age and/or mileage and the concentration of copper in the fluid. Virtual age is utilized to estimate the degree of degradation of the fluid. A reactive test strip is used to measure the concentration of copper ions in the brake fluid in terms of a readily visible color change. The strip is immersed in the fluid and any resulting color change is compared to a color chart and a standard representative of the maximum concentration determined empirically to correspond to the desirable “virtual-age” threshold for fluid replacement. An automated embodiment of the invention includes an optical instrument to compare the color obtained from the test to a predetermined standard and determine whether a fluid change is recommended.

I claim:  
     
       1. A method of establishing service requirements for a brake fluid in a vehicle's brake system as a function of a variable indicative of the fluid's service age and service mileage, comprising the following steps: 
       (a) determining a correlation between said variable and a content of reactive constituent in the fluid;  
       (b) measuring a current value of said content of reactive constituent in the fluid by reaction with a test reactant exposed to said brake fluid:  
       (c) determining a current approximation of said variable on the basis of said correlation; and  
       (d) carrying out a maintenance schedule for the brake system on the basis of said current approximation of the variable indicative of the fluid's service age and service mileage;  
       wherein said reactive constituent is selected from the group consisting of copper, iron, and zinc.  
     
     
       2. The method of  claim 1 , wherein said test reactant includes a reactive strip and step (b) is carried out by immersing the strip in the fluid and by matching a color resulting thereby on the strip with a color chart representing a correlation between color and content of said reactive constituent in the fluid. 
     
     
       3. The method of  claim 1 , wherein said reactive constituent is copper, said test reactant includes a reactive copper strip and step (b) is carried out by immersing the strip in the fluid and by matching a color resulting thereby on the strip with a color chart representing a correlation between color and copper content in the fluid. 
     
     
       4. The method of  claim 3 , wherein said maintenance schedule includes an empirical copper-content threshold of 150 parts per million for replacement of the fluid. 
     
     
       5. The method of  claim 1 , wherein the reactive constituent is iron, said test reactant includes a reactive iron strip and step (b) is carried out by immersing the strip in the fluid and by matching a color resulting thereby on the strip with a color chart representing a correlation between color and iron content in the fluid. 
     
     
       6. The method of  claim 5 , wherein said maintenance schedule includes an empirical iron-content threshold of 50 parts per million for replacement of the fluid. 
     
     
       7. The method of  claim 1 , wherein the reactive constituent is zinc, said test reactant includes a reactive iron strip and step (b) is carried out by immersing the strip in the fluid and by matching a color resulting thereby on the strip with a color chart representing a correlation between color and zinc content in the fluid. 
     
     
       8. The method of  claim 7 , wherein said maintenance schedule includes an empirical zinc-content threshold of 50 parts per million for replacement of the fluid. 
     
     
       9. The method of  claim 1 , wherein an automated device is used in step (c). 
     
     
       10. The method of  claim 1  wherein said brake system is an automotive brake system. 
     
     
       11. A kit for establishing service requirements for a brake fluid in a vehicle's brake system as a function of a variable indicative of the fluid's service age and service mileage, comprising: 
       a test standard representing a correlation between said variable and a metal content in the brake fluid;  
       a test reactant capable of reacting with said metal in the brake fluid and producing an indication of a current metal content in the brake fluid upon exposure of said test reactant with said brake fluid; and  
       a predetermined empirical maintenance schedule for the brake system based on said variable indicative of the fluid's service age and service mileage;  
       wherein said metal is selected from the group consisting of copper, iron, and zinc and said test standard includes a color chart.  
     
     
       12. The kit of  claim 11 , wherein said test reactant includes a reactive strip adapted for immersion in the fluid to produce said indication of a current metal content in the brake fluid. 
     
     
       13. The kit of  claim 11  wherein said metal is copper, said test reactant includes a reactive copper strip, and said test standard includes a copper color chart. 
     
     
       14. The kit of  claim 13 , wherein said maintenance schedule includes an empirical threshold of 150 parts per million of copper for replacement of the fluid. 
     
     
       15. The kit of  claim 11 , wherein said reactive constituent is iron, said test reactant includes a reactive iron strip, and said test standard includes an iron color chart. 
     
     
       16. The kit of  claim 15 , wherein said maintenance schedule includes an empirical threshold of 50 parts per million of iron for replacement at the fluid. 
     
     
       17. The kit of  claim 11 , wherein said metal is zinc, said test reactant includes a reactive zinc strip, and said test standard includes a zinc color chart. 
     
     
       18. The kit of  claim 11 , further comprising an automated device for producing said indication of a current metal content in the fluid, and for establishing maintenance requirements for the brake fluid as a function of said current metal content in the fluid. 
     
     
       19. A brake-fluid dispenser and test kit for replacing brake fluid in a vehicle's brake system as a function of a variable indicative of the fluid's service age and service mileage, comprising: 
       a container with brake fluid;  
       a test standard representing a correlation between said variable and a metal content in the brake fluid;  
       a test reactant capable of reacting with said metal in the brake fluid and producing an indication of a current metal content in the brake fluid upon exposure of said test reactant with said wake fluid; and  
       a predetermined empirical maintenance schedule for the brake system based on said variable indicative of the fluid's service age and service mileage;  
       wherein said metal is selected from the group consisting of copper, iron, and zinc and said test standard includes a color chart.  
     
     
       20. The kit of  claim 19 , wherein said test reactant includes a reactive strip adapted for immersion in the fluid to produce said indication of a current metal content in the fluid.